Woronora Heights residents are ramping up their campaign to stop Sydney Water creating home sites in bushland, which is part of a wildlife corridor linking koala habitats.
In 2020, a koala took up residence immediately adjacent to the proposed development site and other sightings have been reported close by.
A development application (DA) was lodged last year on Sydney Water's behalf for a subdivision of the 32,760 square metre site in Bundanoon Road, and is due to be determined by the Sutherland Shire Local Planning Panel.
Sydney Water told the Leader this week it "remains committed to further consultation with council, and any concerns raised through them will be addressed".
"The project will be further assessed before we proceed further," the statement said.
John Souvleris, a spokesman for residents opposing the DA said, if approved, the DA would have a significant impact on the wild life corridor's connectivity to the E2 Zoned Land (Environmental Conservation Land) Woronora Height, Loftus Valley, Forbes Creek, Crescent Creek, Bonnet Bay and Woronora Valley.
Mr Souvleris said the corridor would be reduced from a width of 355 metres to 261 metres.
"Over the last four months, we have door knocked homes, undertaken letterbox drops and held a street stall over four Saturdays."
Mr Souvleris said 224 individually signed letters had been delivered to Heathcote MP Lee Evans and 220 letters to Water Minister Kevin Anderson.
An on-line petition had 18,000 signatures and a hard copy petition more than 720 signatures, he said.
A Koala Wildlife Corridor Rally will be held on Friday October 21 at 3.30pm in Engadine Town Square.
Dr Catherine Reynolds, a spokeswoman for Sutherland Shire Environment Centre, said the area of bushland leads to a potential wildlife overpass of Princes Highway at Loftus, which might one day be used to provide a connection to Royal National Park.